Metastasis is probably the most important event for determining outcome in cancer patients. The detection of occult metastases in the bone marrow, while known to be clinically important, has not become routine clinical practice. This is due to the technical difficulties and costs involved in the current methods for their collection and detection. Detection of circulating tumor cells (CTC) in the blood is less sensitive than in bone marrow and suffers from the same technical barriers as the detection of tumor cells in the bone marrow, but offers the distinct advantage of being less invasive and better for patient compliance. Therefore, sensitive detection of earliest metastatic spread of tumor in a minimally invasive and user-friendly manner will have a great impact on the clinical management of cancer patients. The currently available methodologies for CTC capture and identification face significant barriers including multiple procedural steps, substantial human intervention, extremely high cost, and importantly, lack of reliability and standardization for the detection methods. We have demonstrated the potential for sized-based tumor cell capture using a parylene-based micropore membrane. We propose to develop this into a microchip device for processing blood, and eventually bone marrow and other fluids like pleural effusions or ascites. This microdevice, coupled with microfluidics, has the potential to revolutionize the approach to tumor cell capture and identification. Further, we propose to develop methods for on-chip characterization of the captured cells. First, in R21 Phase, we will develop and optimize the capture device using a model system to isolate and molecularly characterize cultured cancer cells admixed in blood, followed by a pilot study to examine blood from 45 actual cancer patients with metastatic disease for breast, prostate or bladder cancer. In R33 Phase, we will extend the application of microdevice to assess about 310 patient samples from the same three malignancies, and we will also assess the molecular characteristics of the CTC using the Quantum Dots to understand the biological features of these otherwise rare cells (such as existence of putative stem cell sub-population which may be more malignant). At completion, studies in this project will develop a cost effective on-chip system for capture, identification, and characterization of CTC, easily usable in the clinical setting. [unreadable] [unreadable] [unreadable]